User defined types: Problems with ref

[FreeSlave]

On Thursday, 23 January 2014 at 15:24:19 UTC, Chris wrote:
> Here's what I'm trying to do.
>
> struct Element(T) {
>     T x;
>     T y;
>
>     public void setX(T value) {
>       x = value;
>     }
>     // More fancy functions ...
> }
>
> I store Element(s) in an array and want to pass each one by 
> reference, which does not work.
>
>
> class Tree {
>
>     Element!string[] elements;
>
>     public ref auto createElement(string name) {
>       elements ~= Element!string(name);
>       return elements[$-1];
>     }
> }
>
> in main:
>
> auto tag = Element!string("first");
>
> The elements in Tree.elements and the ones in main are not the 
> same, instead I obtain a copy of each.
> How can I make them refer to the same Elements? If I have to 
> add a .ptr property to Element, how do I do that? Is that 
> possible at all or did I shoot myself in the foot with the 
> template?

You can use pointer

Tree tree = new Tree();
Element!(string)* element = &tree.createElement("first");

& is to get address of returned value element.

You also can rewrite your function like this:

public Element!(string)* createElement(string name) {
         elements ~= Element!string(name);
         return &elements[$-1];
     }

to return pointer without need to get address on caller side.